Related Party Transactions - Additional information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended				9 Months Ended				12 Months Ended
	Jul. 06, 2004	Sep. 30, 2019		Sep. 30, 2018		Sep. 30, 2019		Sep. 30, 2018		Dec. 31, 2018
Investments in and Advances to Affiliates
Dividends, cash		$ 3,990	[1]	$ 4,240	[1]	$ 12,112	[2]	$ 12,809	[2]
Preferred units, preferred partners' capital accounts		30,000				30,000
Sale of stock, consideration received on transaction	$ 30,000					76,000				$ 100,700
Unfunded investment contribution liabilities		0				0
SLP Units
Investments in and Advances to Affiliates
Dividends, cash		$ 500		$ 1,500		500		$ 1,500
Joint Venture [Member]
Investments in and Advances to Affiliates
Sale of stock, consideration received on transaction						$ 1,200				$ 1,300
Membership interest						2.50%				2.50%
East 11th Street
Investments in and Advances to Affiliates
Redemption of preferred investments						$ 17,000
3002 39th Avenue
Investments in and Advances to Affiliates
Redemption of preferred investments						10,000
Miami Moxy
Investments in and Advances to Affiliates
Additional investments in and advances to affiliates at fair value gross additions						$ 2,300

[1] Distributions per share were $0.175.

[2] Distributions per share were $0.525.